It's been a relatively mild summer here in New York, but the last few days have been hot, hot, hot. Left to my own devices I would be splayed out in front of our a.c. all day long, but my 14-month-old (seemingly impervious to the heat) wants to be out. Already tuckered out from a walk and the playground (me, not him) I decided to set up an improvisational water table in the backyard so he could be out and I could get off my feet.
I emptied out a plastic under-bed storage box, filled it with cool, sudsy water (baby manicure!) and threw in a few bath toys. To counterbalance the weight of the kid and the water on the table I put the base of our very heavy umbrella on the other side of the table. The angle for him to reach in and play was not particularly ergonomic, but he didn't seem to mind.
This worked out pretty well - for younger children who have traditional high chairs you could fill their tray with water and let them splash around.